The gaze direction of a person may be used to select options displayed on a computer screen. Thus, an eye tracker device providing information on the gaze direction may be used, for example, as a pointing and selecting device instead of a computer mouse.
When light impinges on the eye, several reflections occur on the boundaries of the lens, cornea and retina. These reflections provide reflection spots known as the Purkinje images. The reflection from the outer corneal surface provides the first Purkinje image, also called as the glint. The orientation of the eye may be determined based on the position of the pupil with respect to the position of the first Purkinje image.
U.S. Pat. No. 4,836,670 discloses an eye movement detector, which utilizes an infrared-emitting diode mounted coaxially in front of the lens of an infrared-sensitive camera for acquiring an image of the eye. The reflected light causes a glint from the surface of the cornea. The image of the eye is analyzed to determine the location of the pupil's center and the location of the glint relative to each other and this information is used to determine the gaze direction.